Expression of tissue inhibitor of metalloproteinases-3 messenger RNA and protein in porcine endometrium during implantation

Recent evidence points to a stromal decidualization-like response in the pregnant porcine uterus. The objective of this study was to evaluate expression of tissue inhibitors of metalloproteinase-3 (TIMP-3), a sensitive indicator of endometrial stromal decidualization, in endometrium of pregnant sows and to further investigate this phenomenon. Real-time PCR, Western blot and immunostaining analysis were used to study TIMP-3 expression between/at attachment sites of endometrium of Days 13, 18 and 24 pregnant sows. The results indicate that TIMP-3 protein expression was lowest by Day 13 compared with Day 18 (P<0.01) and 24 (P<0.01), and the expression was higher at attachment sites than between attachment sites on Day 13 (P<0.01) and 18 (P<0.01). TIMP-3 intensive immunostaining was observed in stroma of endometrium on Days 13, 18 and 24, and the staining at attachment sites was stronger than between attachment sites. Collectively, these results suggest the crucial role of TIMP-3 in successful implantation and embryo survival and indicate the endometrial stromal decidualization-like in pigs.